1. Field of the Invention
This invention relates to a signal processing circuit of an electrostatic capacity type touch panel.
2. Description of the Related Art
The electrostatic capacity type touch panel has been known as an input device to various kinds of electronic devices such as a mobile phone, a portable audio device, a portable game console, a television and a personal computer.
FIG. 12 is a plan view of the electrostatic capacity type touch panel 101. The touch panel 101 is formed on a glass substrate 100, as shown in the drawing. A plurality of sensor circuits 102A and 102B made of IC chips is disposed on a periphery of the large touch panel 101 using a COG (Chip On Glass) technology.
The sensor circuits 102A and 102B detect a change in a capacitance of a capacitor located at a touch position on the touch panel 101. Results of the detection are processed by a microcomputer incorporated in each of the sensor circuits 102A and 102B so as to determine coordinates of the location of the touch position. Technologies mentioned above are disclosed in Japanese Patent Application Publication No. 2005-190950, for example.
However, there is a problem that components are duplicated and a cost of the components is increased since each of the plurality of sensor circuits 102A and 102B incorporates the microcomputer respectively in the conventional electrostatic capacity type touch panel.